X-ray images using films have been widely used heretofore in medical settings. However, the X-ray image using a film provides analog image information, and in recent years, digital radiation detectors such as computed radiography (CR) and flat panel radiation detectors (flat panel detectors: FPDs) have been developed.
In a flat panel X-ray detector (FPD), a scintillator panel is used for converting a radiation into visible light. The scintillator panel contains an X-ray phosphor such as cesium iodide (CsI), the X-ray phosphor emits visible light in response to an applied X-ray, and the emitted light is converted into an electric signal by a TFT (thin film transistor) or a CCD (charge-coupled device) to thereby convert X-ray information into digital image information. However, the FPD has a problem of low S/N ratio. This is attributable to scattering of visible light by the X-ray phosphor itself when the X-ray phosphor emits light, etc. For reducing influences of the scattering of light, methods of filling an X-ray phosphor in cells divided by a barrier rib have been proposed (Patent Documents 1 to 4).
The shape of the barrier rib varies depending on a pitch, but the width is approximately 5 to 40 μm, and the height is approximately 100 to 800 μm.
The method which has been heretofore used as a method for forming the barrier rib is a method of etching a silicon wafer, or a method in which a glass paste, a mixture of a pigment or a ceramic powder and a low-melting-point glass powder, is pattern-printed in multiple layers using a screen printing method, and then fired to form a barrier rib. However, in the method of etching a silicon wafer, the size of a scintillator panel that can be formed is restricted by the size of a silicon wafer, and a scintillator panel having a large size of, for example, 500 mm square cannot be obtained. A plurality of small-size panels should be arranged for making a large-size panel, but production of a scintillator panel in this way is difficult in terms of accuracy, and it is difficult to prepare a large-area scintillator panel.
In the multi-layer screen printing method using a glass paste, processing of high accuracy is difficult due to a dimensional variation of a screen printing plate, etc. Further, when multi-layer screen printing is performed, a definite barrier rib width is required for enhancing the strength of a barrier rib in order to prevent destructive defects of the barrier rib. However, if the width of the barrier rib increases, a space between barrier ribs becomes relatively small, so that a volume available for filling an X-ray phosphor decreases, and the filling amount is not uniform. Therefore, a scintillator panel obtained in this method has the disadvantage that the amount of an X-ray phosphor is so small that the luminescence is reduced, and luminous unevenness occurs. This disadvantage makes it difficult to photograph sharp images in photographing in a low radiation dose.
That is, for preparing a scintillator panel which has high luminous efficiency and provides sharp images, a technique for processing a barrier rib, which is capable of processing the barrier rib with high accuracy over a large area and narrowing the width of the barrier rib, and a technique for preventing visible light, which is emitted by an X-ray phosphor, from being leaked to outside are required.